1. Field of the Invention (Technical Field)
The present invention concerns systems for sensing characteristics of motor vehicle occupants for purposes such as deployment of air bags during vehicle crashes. More particularly it concerns systems in which the system operation is affected not only by information about the motion of the vehicle caused by crash forces, including angular acceleration, but also measured data concerning the motion of the passenger, so that the system will operate in a manner to minimize the risk of serious injury to the passenger, and will not operate when the air bag deployment would not likely be beneficial.
2. Background Art
Automobile air bag systems are a well known means of attempting to reduce the likelihood of serious injury to passengers in collisions. These systems are designed to very quickly inflate an air bag in front of a passenger during a collision, so as to hopefully prevent the passenger from colliding with hard objects in the passenger compartment interior, particularly the steering column and/or the dashboard. Such systems typically sense that the vehicle is involved in a collision, by using an accelerometer to sense sudden deceleration of the vehicle. Rapid inflation of the air bag may be obtained by electrical ignition of a pyrotechnic substance which rapidly generates a volume of gas sufficient to inflate the air bag, or by electrical opening of a valve for release of compressed gas stored in a chamber which is part of the air bag system.
The performance of an air bag system, in terms of its success or failure in preventing serious passenger injury, may be critically dependent on facts concerning the initial position and subsequent motion of the passenger, which are not made known to the system by an accelerometer which senses deceleration of the vehicle as a whole. Passenger head motion is particularly important, due to the seriousness of head injuries. For example, if the passenger is seated too far forward, or has his/her head too far forward, occupying the space into which the air bag will deploy, the passenger may be seriously injured by the deployment of the air bag intended to prevent passenger injury. So there is clearly a need for passenger position sensing apparatus, which can prevent air bag deployment when the passenger is already too far forward when the collision begins.
But even if the passenger is not too far forward at the beginning of the collision, the passenger will tend to move rapidly forward, with the passenger's head leading that motion, relative to the vehicle, as the vehicle rapidly decelerates, and will tend to move into the air bag deployment space, at least in the case of forward collisions, and may be too far into the air bag deployment space, before the completion of air bag deployment, to escape injury from the air bag deployment. There are a number of factors which may strongly influence the forward motion of the passenger, in addition to initial position, in ways which may vary markedly from one passenger to another. The relative forward motion of the passenger will depend strongly on whether the passenger has secured a seat lap belt and/or shoulder harness prior to the collision. The passenger's motion may also be influenced somewhat by the strength of any tensing up reaction the passenger has to the collision, i.e., instinctively pushing forward with the feet against the floorboard to restrain forward motion of the body. Such a protective reaction may vary greatly from one passenger to another, and may be greatly reduced or wholly absent if the collision is too sudden, so that the passenger has no time to react, or if the passenger is intoxicated or otherwise impaired. Also variation of the crash intensity by itself will cause considerable variation in passenger acceleration. So there is a need for systems which measure the position vs. time of the passenger, particularly head motion, and analyze that information in making the yes or no decision on air bag deployment. Although systems are known which measure passenger motion, as described in documents filed with applicant's Information Disclosure Statement, applicant is not aware of such a system employing an overhead array of capacitive coupling proximity sensors, as in the present invention, to continuously determine passenger position by triangulation, and determine passenger acceleration by means of a microprocessor which analyzes signals indicative of passenger distance from each sensor of the array, and changes of said distances with time. Overhead sensors offer an advantage over those previously known systems having beam--emitting sensors located in front of the passenger, as in air bag systems with acoustic sensors mounted on the steering column, for which the beam from the sensor will at times by blocked from operating by the hands and/or forearms of the driver.
The use of an array of capacitive coupling proximity sensors offers advantages over beam--emitting sensors, in an air bag system, since each capacitive coupling sensor functions by sensing the change in the capacitance of a capacitor, caused by the nearby presence of a person, an effect which is essentially instantaneous (since propagated at light speed), rather than requiring a finite, non--negligible beam travel time as in the case of an ultrasonic position sensor, and since the capacitive coupling sensor does not require transmission and detection of a beam which might be blocked. And the use of the overhead array of capacitive coupling proximity sensors, the signals from which are analyzed by the microprocessor, allows essentially instantaneous and continuous monitoring of passenger position and motion through triangulation based on the distances of the passenger to the various sensors of the array, so that the overhead sensor array can be used to accurately and continuously determine fore--aft, diagonal, and lateral passenger motion. Since the passenger's head will be closest to the overhead sensors, this method will be particularly sensitive to passenger head motion.
The present invention also addresses a need for an air bag system sensitive to angular vehicle acceleration, for both crash confirmation purposes and also to prevent air bag deployment in the case of a vehicle rollover, in which case air bag performance may be unreliable and deployment is undesirable. This need is met through use of a three axis vehicle rollover sensor, the output of which is analyzed by the microprocessor.
The present invention also addresses a need for an air bag system that will provide protection against injury of a forwardly positioned passenger, which might otherwise be caused by the air bag deployment, in particular an infant sitting in a conventional rear--facing infant car seat, conventionally positioned with the child's head rather far forward, where the child may suffer a serious head injury during air bag deployment. As detailed below, this need is met by the provision of an air bag which, when inflated and deployed, has two principal chambers with a reentrant slot between them, which slot can accommodate the infant in the car seat, and which geometry allows deflection of the rearmost of the two chambers by the car seat and infant, to reduce the force of impact with the passenger and thus reduce the risk of such an injury.
Since the design of automotive air bag systems continues to evolve, as more knowledge is gained about the dynamics of crashes, including problems associated with variations in passenger motion during a crash, there is a need, for crash investigation purposes, for a system which can record the vehicle and passenger motion during the crash process, particularly passenger head motion. This need is met by the present invention, through the provision of recording means in the microprocessor connected to the sensors which detect vehicle and passenger motion.